Does anyone know how much gravity rice syrup solids add to the wort? The online Recipe Calculator doesn't include it as a choice for adjuncts. Is the sugar content close enough to corn sugar or dried malt extract that I could just use their values?

I ran a check usind the BeerToolsPro software program, and it shows 36 points per pound of "Rice Syrup" and the same value for "Rice Extract", without indicating whether the extract is dried extract or liquid extract. Since your question is about "rice syrup solids", which I've never used, I presume that you are referring to something that is "dry", and would need to make a conversion based on percentage of water remaining in the 'syrup'. I have no idea what that would be, but this is the best I can do and perhaps it will be enough to start you in the right direction.

Can't your supplier provide you with some data. Also, I'd imagine a google search might reveal the answer, but I'll leave that up to you to do.